@Faeldrin A guy having earrings isn’t all that unusual(I’m one of them), but I do think it’s a woman. The words he/she weren’t used, so I think it’s kept ambiguous on purpose.
Surely some basic chicken dish or spaghetti bolognese wouldn't have been so expensive. In a certain sense he's actually wasting the senpai's money by only ordering a salad when she was worried about his lunch. A steak might have been a bit much under those circumstances.
@ebonarm She wanted to do what her senpai did for her, bringing the drinks and all. I think.
That or she wanted to teach him that the kouhais must bring the drinks because some senpais want them to.